Contralateral mastectomy improves survival in women with BRCA1/2-associated breast cancer.

BRCA1/2 mutation carriers with breast cancer are at high risk of contralateral disease. Such women often elect to have contralateral risk-reducing mastectomy (CRRM) to reduce the likelihood of recurrence. This study considers whether CRRM improves overall survival. 105 female BRCA1/2 mutation carriers with unilateral breast cancer who underwent CRRM were compared to controls (593 mutation carriers and 105 specifically matched) not undergoing CRRM and diagnosed between 1985 and 2010. Survival was assessed by proportional hazards models, and extended to a matched analysis using stratification by risk-reducing bilateral salpingo-oophorectomy (RRBSO), gene, grade and stage. Median time to CRRM was 1.1 years after the primary diagnosis (range 0.0-13.3). Median follow-up was 9.7 years in the CRRM group and 8.6 in the non-CRRM group. The 10-year overall survival was 89 % in women electing for CRRM (n = 105) compared to 71 % in the non-CRRM group (n = 593); p < 0.001. The survival advantage remained after matching for oophorectomy, gene, grade and stage: HR 0.37 (0.17-0.80, p = 0.008)-CRRM appeared to act independently of RRBSO. CRRM appears to confer a survival advantage. If this finding is confirmed in a larger series it should form part of the counselling procedure at diagnosis of the primary tumour. The indication for CRRM in women who have had RRBSO also requires further research.